STRUCTURAL ELUCIDATION AND CONFORMATIONAL-ANALYSIS OF NEW LIGNAN BUTENOLIDES FROM THE LEAVES OF BUPLEURUM-SALICIFOLIUM

From the leaves of Bupleurum salicifolium two new benzylidene-benzyl-g amma-butyrolactone-type lignans salicifoline (2) and isosalicifoline ( 3) were isolated. The dibenzyl-butyrolactone (-)-epinortrachelogenin ( 1) was also isolated and it is the first time than this lignan has bee n obtained from a natural source. Their structures were determined by means of H-1 and C-13 NMR spectroscopic studies, including H-1-C-13 he teronuclear correlation (HETCOR), long range correlation spectra with inverse detection (HMBC), and chemical evidence. A study of the confor mational analysis of these lignans using Molecular Mechanics Calculati ons is also included.